Abstract Body (Do not enter title and authors here): Introduction
Fat Embolism Syndrome (FES) is a rare but potentially life threatening complication of sickle Cell Disease (SCD). While pulmonary involvement is typical, paradoxical embolization through a patent foramen ovale (PFO) may result in cerebral fat embolism and acute neurologic decline. We present a case highlighting this uncommon but critical mechanism.

Case Presentation
A 43 year old female with homozygous sickle cell disease (HgbSS) presented with severe generalized pain (9/10) in the lower back, abdomen, and bilateral lower extremities. Her hospital course was complicated by fever (101 F), tachycardia (HR 190s), progressive lower extremities weakness, hypoxic respiratory failure requiring 5 L/min nasal cannula, and acute encephalopathy, prompting ICU transfer.
Brain MRI revealed innumerable punctuate foci in the bilateral centrum semiovale, consistent with cerebral fat embolism. Emergent red blood cell exchange reduced HbS from 82% to 27%. Transthoracic echocardiography with bubble study demonstrated a PFO with right to left shunting.
She was managed with aspirin, station therapy, IV hydration, and pain control. Her neurologic and respiratory status improved, and subsequently discharged on room air with hematology and cardiology follow up for potential PFO closure.

Discussion
In SCD, vaso-occlusive crisis can lead to bone marrow ischemia and necrosis, releasing fat globules into the venous circulation. Normally, these emboli are filtered out through pulmonary vasculature however, in patients with PFO, a right to left intracardiac shunt enables these fat emboli to bypass the lungs and reach systemic circulation including the brain.
This case illustrates a rare, two step mechanism of cerebral FES in SCD. First, bone marrow derived fat embolism during crisis, second, paradoxical embolism via an intracardiac shunt. The triad of encephalopathy, hypoxia, and MRI characteristic findings should prompt an evaluation for cerebral FES, including echocardiography to assess for PFO.

Conclusion
In SCD patients with acute neurological changes, clinicians should maintain a high suspicion for cerebral FES. Early neuroimaging, red cell exchange, and structural heart evaluation are essential. Identification of a PFO can provide key insight into the paradoxical mechanism and further influence long term management.